Blown stretch wrap film generally has higher tensile strength than cast film. Linear low density polyethylene ("LLDPE") is much more useful than low density polyethylene ("LDPE") as the film-forming component of blown stretch wrap films. However, a cling additive must be blended with LLDPE since LLDPE film does not exhibit a high level of cling when stretched in the typical usage to about 200 percent elongation. The film made from the composition of the present invention generally also has an unwinding noise not greater than the unwinding noise of the neat ethylenic polymer. This is important in light of the OSHA noise workplace restrictions.
June 1992 U.S. Research Disclosure 33875 discloses that a polyolefin having a Brookfield Thermosel Viscosity of about 6,000 mPa.cndot.s at 190.degree. C., and a needle penetration hardness of about 35 dmm and a polyolefin having a Brookfield Thermosel viscosity of 2300 mPa.cndot.s at 190.degree. C. and a needle penetration hardness of 20 dmm are useful in cast and blown LLDPE and LDPE film. The applicant has found that blown polyethylene based stretch cling films containing these polyolefins have little or no peel cling strength at 200 percent elongation. The applicant has previously disclosed a very low viscosity partially crystalline propylene-ethylene cling additive for EVA, LDPE, and LLDPE stretch film composition. The disclosed propylene-ethylene cling additive comprises a partially crystalline propylene-ethylene copolymer having 10 to 40 weight percent ethylene units, within the viscosity range of 1 to 2,000 mPa.cndot.s at 190.degree. C. The known propylene-ethylene copolymer cling additive has a needle penetration hardness less than about 150 dmm at 23.degree. C. The film composition disclosed therein is more useful for film blowing than are film compositions made with the above higher viscosity polyolefins. However, the previously disclosed blown film has a peel cling strength that is lower than cast films containing the above higher viscosity polyolefin cling additives.
In light of the above, it would be desirable to have a polyethylene-based film having the combination of excellent blown film properties as well as relatively high peel cling strength.